Me wrote:

....
What do you suggest is best replacement for the oil?

auto transmission fluid?
brake fluid?
power steering fluid?
motor oil?
....

"Best" would be to go buy some (it's inexpensive) and you could have
gone and been back several times over by the time you asked...

As someone else noted, don't trust a jack that's leaking w/ anything
even close to a pinkie-smash...